I’ve tried to replicate it in a test App on my profile, i get the same error. Tried a few attemps, but same. Just guessing if the problem could be a security restriction on FB iframe environment with your way of loading the xml:

.../cecelia/xml/facebooktemplate.xml?noCache=1298672749…

Try to skip the “noCache” parameter. Same for CSS file.
Maybe i could be wrong, but give it a try.

50andJACK said
I don’t have a noCache thingie. Plus, it works on my end, and he says he can’t get any flash file to work as an iFrame. Works fine for him as FBML though. Weird.

My httpFox displays the xml loading the way i sent you above, with the noCache parameter. I’ve tested on my fb file and it just displays the GET of the plain xml. I see you have css and xml paths as flashvars in the index.html, maybe the plugin create the noCahe automatically for flashvars? Just guessing… . Give a try to just parse them directly in the swf, not using flashvars. Almost sure here resides the GET block inside FB App. Maybe the FBML does not have these restrictions so it just works well.